dir: ignore trailing spaces in exclude patterns

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitignore.txt

@@ -77,6 +77,9 @@ PATTERN FORMAT
    Put a backslash ("`\`") in front of the first hash for patterns
    that begin with a hash.
 
+ - Trailing spaces are ignored unless they are quoted with backlash
+   ("`\`").
+
  - An optional prefix "`!`" which negates the pattern; any
    matching file excluded by a previous pattern will become
    included again.  If a negated pattern matches, this will

dir.c

@@ -463,20 +463,23 @@ void clear_exclude_list(struct exclude_list *el)
 	el->filebuf = NULL;
 }
 
-static void check_trailing_spaces(const char *fname, char *buf)
+static void trim_trailing_spaces(char *buf)
 {
-	int i, last_space = -1, len = strlen(buf);
+	int i, last_space = -1, nr_spaces, len = strlen(buf);
 	for (i = 0; i < len; i++)
 		if (buf[i] == '\\')
 			i++;
-		else if (buf[i] == ' ')
+		else if (buf[i] == ' ') {
+			if (last_space == -1) {
 				last_space = i;
-		else
+				nr_spaces = 1;
+			} else
+				nr_spaces++;
+		} else
 			last_space = -1;
 
-	if (last_space == len - 1)
-		warning(_("%s: trailing spaces in '%s'. Please quote or remove them."),
-			fname, buf);
+	if (last_space != -1 && last_space + nr_spaces == len)
+		buf[last_space] = '\0';
 }
 
 int add_excludes_from_file_to_list(const char *fname,
@@ -530,7 +533,7 @@ int add_excludes_from_file_to_list(const char *fname,
 		if (buf[i] == '\n') {
 			if (entry != buf + i && entry[0] != '#') {
 				buf[i - (i && buf[i-1] == '\r')] = 0;
-				check_trailing_spaces(fname, entry);
+				trim_trailing_spaces(entry);
 				add_exclude(entry, base, baselen, el, lineno);
 			}
 			lineno++;

t/t0008-ignores.sh

@@ -779,18 +779,18 @@ test_expect_success PIPE 'streaming support for --stdin' '
 #
 # test whitespace handling
 
-test_expect_success 'trailing whitespace is warned' '
+test_expect_success 'trailing whitespace is ignored' '
 	mkdir whitespace &&
 	>whitespace/trailing &&
 	>whitespace/untracked &&
 	echo "whitespace/trailing   " >ignore &&
 	cat >expect <<EOF &&
-whitespace/trailing
 whitespace/untracked
 EOF
+	: >err.expect &&
 	git ls-files -o -X ignore whitespace >actual 2>err &&
-	grep "ignore:.*'\''whitespace/trailing   '\''" err &&
-	test_cmp expect actual
+	test_cmp expect actual &&
+	test_cmp err.expect err
 '
 
 test_expect_success 'quoting allows trailing whitespace' '